Industrial fermentation broths, hydrolysates, and waste streams are a source of large amounts of carboxylic acids, including organic acids such as succinic acid and as well as amino acids. These carboxylic acids can be used in a number of important commercial applications.
For example, succinic acid is a four-carbon, dicarboxylic acid with the potential to become an important commodity chemical. Succinic acid can serve as an intermediate in the synthesis of many important intermediate and specialty chemicals for the consumer product industries. As a commodity chemical, succinic acid could replace many of the benzene class of commodity and intermediate petrochemicals, resulting in a large reduction of pollution from the manufacture and consumption of over 250 benzene derivative chemicals. Succinic acid is used as a food additive, plant growth stimulator, as an intermediate in the manufacture of pharmaceuticals, as well as polymers and resins for lacquers, dyes, and perfumes.
Currently, succinic acid is produced petrochemically from butane through maleic anhydride. Almost all of the succinic acid consumed in the United States is imported from overseas. Presently, the world market for succinic acid is 100 million pounds annually.
Succinic acid is co-produced in small quantities during corn fermentation in wet-milling ethanol production. It can also be produced from a variety of agricultural and forestry raw materials, such as starch crops and cellulosic sugars. Development of a cost-effective process for purifying this important compound from would provide more than 100 million bushels of an additional value-added commodity outlet for corn alone.
Methods exist for obtaining high purity carboxylic acids from fermentation broths. However, these methods involve numerous operations that make the process prohibitively expensive for commercialization.
One means by which carboxylic acids can be separated from other compounds such as sugars, for example, is through anion exchange chromatography. When unprotonated, the carboxyl group has a negative charge that allows ionic bonding with positively charged moieties on the anion exchange resin, and other materials are removed by washing the resin with water. Generally, the desired anions are released from the anionic exchange resin by washing the column with a solution of a base such as sodium hydroxide. However, this method causes the release of the molecule of interest in its salt form, rather than in its acid form. Therefore, if the acid form of the molecule is desired, it is necessary to include an acidification step and additional purification steps, which contributes significantly to the cost of purifying the acid. The commercial viability of using industrial fermentations, hydrolysates, and waste streams as a source of carboxylic acids depends upon a cost-effective means for recovering purified carboxylic acids from these sources.
What is needed in the art is a cost-effective method for the purification of carboxylic acids.